Pentaerythrityl tetramine (PETA) is an extremely useful material, having known utility in the synthesis of high melting spiro polyamides, the cure of epoxy resins, the isolation and purification of copper, rare earths and other metals and, in combination with air and other oxidizing agents as an etchant of iron, steel, stainless steel and copper. The only published method for synthesizing PETA of which the inventor is aware, is set forth in Litherland and Mann, Journal of The Chemical Society, 1938, page 1588. This procedure is laborous, time-consuming, expensive, hazardous and low-yielding.
Recently, a method for synthesizing PETA by the ammonolysis of the corresponding pentaerythrityl tetrachloride (PETC) at temperatures in the range of 160.degree.-180.degree. C and at pressures of 1000 psi and over in an excess of methanolic ammonia was developed. This process constituted a substantial improvement over the prior art teachings of Litherland and Mann; however, the yields were relatively low (10-30% of the theoretical yield) and even at the high pressures employed, the reaction proceeded at a much slower rate than would be desirable. According to my invention, I have discovered that certain materials act as catalysts for this ammonolysis reaction, substantially increasing the percentage of conversion and substantially decreasing the reaction time. Since the process must be carried out in high pressure equipment and the reactants are extremely corrosive even to the stainless steel normally used in this equipment, the shortening of the reaction time is advantageous for reasons other than the savings in processing time that are obtained.
It is, accordingly, an object of this invention to provide catalysts for the ammonolysis of PETC.
It is another object of this invention to provide a process for the preparation of PETA by the ammonolysis of PETC.
These and other objects of the invention will be readily apparent from the following description.